THE GIST

— Government agencies will be monitoring for release of plutonium in case of an accident during Saturday's Mars rover launch.

— Launch is scheduled for 10:02 a.m. EST from Cape Canaveral Air Force Station in Florida.

— The new robot draws electricity from the heat given off during the natural decay of radioactive plutonium.

NASA is preparing a robotic probe for launch this weekend to search for life's habitats on Mars, but it is the health of people on Earth that is of immediate concern.

The Mars Science Laboratory, nicknamed Curiosity, is powered by the radioactive plutonium isotope Pu-238, which generates heat as it naturally decays. The heat is tapped to produce electricity for the rover's systems and science instruments.

NASA says the chance plutonium will escape into Earth's atmosphere is very remote, given the perfect track record of the Atlas 5 rocket that will be used to launch Curiosity into space.

In addition, the 10 pounds (4.5 kilograms) of plutonium inside the probe is laced into ceramic pellets, designed to break apart into pieces, like a coffee mug, rather than disperse as dust into the air. The plutonium also is encased in a capsule of iridium and wrapped in carbon fibers to absorb heat.

Overall, the chance plutonium will be released during launch is 1 in 420, Randall Scott, director of NASA's Radiological Control Center at the Kennedy Space Center, told Discovery News.

During liftoff, 30 radiation detectors placed throughout the region surrounding the Cape Canaveral Air Force Station launch site, will be taking air samples and reporting measurements real-time to Scott's team.

"Most people will not notice the monitors," added NASA's Steve Brisbin, who is coordinating among the half-dozen federal, state and local government agencies responsible for public safety during launch.

Curiosity's plutonium is inside what is called a radioisotope thermoelectric generator, or RTG. Similar devices have been used on spacecraft since the early days of the space program, including the Apollo moon missions, the Mars Viking landers and the Voyager probes, now heading into interstellar space. The Saturn-orbiting Cassini spacecraft is nuclear powered, as is NASA's Pluto-bound New Horizons probe.